In modern commercial environments, a marking system generally known as barcodes is frequently used to mark inventory with a product identifier encoded as a printed code consisting of black bars on a white background that can be read and decoded reliably by an inexpensive scanner. There are numerous uses for barcodes. One common application is marking products for retail sale with an appropriate barcode. The barcode is later scanned at a point of sale terminal. The scanner and associated computer decode the product identifier from the barcode, and then use the decoded product identifier to look up the price and product name and description from a computerized database, which is then input directly into the point of sale terminal. The information thus received can printed on the customers sales receipt, and can be used for inventory accounting and other related purposes.
Most barcodes tend to look alike to a human observer. The encoded information in a barcode is generally stored in the width of adjacent black bars on a white background. The width of the bars and space between the bars varies widely. A human observer is not able to easily see such variations in width, but electronic scanners, in conjunction with a computer, can accurately read and decode barcodes. In order to increase the reliability of barcodes systems, redundant information is often encoded in the barcode so that the reading system has additional information that can be used to verify that a reading is accurate.
There are numerous schemes for encoding and decoding barcodes. The different encoding schemes for barcodes are called symbologies. Some symbologies print a barcode in the smallest space possible. Others include varying amounts of redundant data that increases the reliability of accurately reading data at the expense of large printed codes. Well known symbologies include numeric only symbologies including a number of UPC-based symbologies such as UPC-A, UPC-E, EAN-13, EAN-8, Bookland, Code 11, Postnet, and Codabar. Additionally, there are a number of alphanumeric symbologies such as Code 128, Code 39, and Code 93. Alphanumeric symbologies can encode letters as well as numbers.
For a barcode system to work, the device for printing barcodes and the devices to read the corresponding barcodes must agree upon and understand the symbology being deployed. A feature of most symbologies is a special bar pattern for starting and ending a single barcode. Many symbologies also include an additional xe2x80x9ccheck digitxe2x80x9d, typically printed before the stop code, that the reading/scanning system uses to verify the barcode was read correctly. xe2x80x9cCheck digitxe2x80x9d is typically a single encoded digit, but the term is used here in the general sense to include any kind of redundant characters, including alphanumeric characters and multiple character strings. These check digits are created by a number of different schemes, depending on the rules of the symbology being deployed. Although human manual computation of check digits can be done, it is highly undesirable to do so because such computation is error prone and requires a very technical understanding of the symbology. It is preferable and customary to use a computer to calculate the check digit.
Each set of black bars that represents a single encoded character of a barcode is called a glyph, and a typical glyph is printed by printing a number of adjacent black bars, accurately spaced with a predetermined amount of white space, according to the symbology being deployed. Historically, barcodes needed to be printed with special printing devices, but modern computing devices, including laser and inkjet printers now have sufficient printing capabilities to print high quality barcodes. Numerous modern computer applications on popular computer systems can now print barcodes for reading by a suitable device. Unfortunately, because of the large number of symbologies, most applications do not support all symbologies, and many application programs do not directly support any symbology. A limited number of applications provide extensive barcode support, but such applications tend to be expensive and difficult to maintain because of the complexity and variety of symbologies. A larger number of applications support partial encoding in an indirect manner. Typically, such programs allow usage and specification of data rendered in various fonts supported by a particular printer. Special bar code fonts are available. Applications can specify that a particular string (the product identifier) is to be rendered in the special bar code font. The scheme requires the user of the application to explicitly select a barcode font available on an associated printer and then explicitly provide the start character, the stop character, and the check digit in the barcode font.
Because of the complexity of barcode encoding, it is desirable to separate the bar encoding technology from the application program. Such modularity allows the barcode encoding technology to be provided by one entity having the requisite knowledge of barcode technology, and the application logic to be provide by another entity having the requisite knowledge for the particular application. Thus as new symbologies are invented, the barcode module can be updated without requiring the application developer to modify the application. Furthermore, this modularity allows application users to limit the supported symbologies to a specific subset of available symbologies; this can lead to both a reduction in complexity and a reduction in cost, since there is generally additional cost in providing support for numerous symbologies.
There are at least three well known schemes for separating application program logic from barcode logic. The first is to provide a barcode font, and then rely on the user of an application to select the barcode font, and explicitly provide any required start characters, stop characters, or check digits. A commercial example of this scheme is Altek Bar Code TrueType fonts by ABC Fonts.
The second scheme is to provide a separate barcode encoder tool, typically a separate program on the host computer. In this scheme, the product identifier is entered into the barcode encoder tool either manually or through a textual cut-and-paste operation. The barcode encoder tool then encodes the product identifier into the corresponding barcode, the resulting barcode must be transferred back into the main application program, typically through a cut-and-paste operation. This scheme is undesirable because it is cumbersome and it requires human intervention between the application and barcode program. A commercial example of a product deploying this scheme is Bars and Stripes by a company of the same name.
A third scheme is to provide a barcode encoder in a printer. This scheme requires a predefined barcode font to be installed on the printer. This scheme has a significant advantage over the other schemesxe2x80x94the barcode encoding is done automatically without human intervention. In particular, start characters, stop characters, and check digits are all provided automatically by the encoder in the printer. This scheme is limited to environments having printers so equipped and having the necessary barcode fonts. Many popular printers, such as Hewlett Packard laser printers, provide a slot for a DIMM, a custom memory chip that allows the capabilities of a printer to be expanded by a third party. DIMM""s have been created to provide knowledge of certain symbologies for certain printers, thus providing easier barcode encoding for applications in that environment. Unfortunately, not all printers can be enhanced in this manner, and creating such a DIMM is very technical, usually requiring computer programming for the native processor of the particular printer. Of course, there is considerable cost to having a barcode enhanced printer. A commercial example of this scheme is Hewlett-Packard printers that provide for external DIMM""s; the DIMM""s themselves are provided by third parties such as JetCAPS.
What is needed is the ability to provide modularized barcode encoding technology in a manner independent of either application programs or printers such that barcodes, including the start character, stop character and check digit can be encoded automatically without human intervention.
The present invention overcomes the limitations of the prior art by teaching a novel bar encoding method and system that allows barcode encoding technology to be added to the host computer, independent of either the application or the printer technology. In the preferred embodiment, the technology is deployed using a print monitor in the Microsoft Windows family of operating systems. In another embodiment the present invention teaches deployment in a Unix/Linux print daemon. Although the technology is useful in these two embodiments, the technology is not limited to them. Rather the technology is deployable in any host computer having an operating system that allows print data between an application program and the printer to be examined and modified.